[Feature] FreezeTag mode as an option for Elimination

[NeonKnightOA]

Related thread: http://openarena.ws/board/index.php?topic=5440.0

I have worked in the past on porting the Freezetag mod to OA code, though I've lost a bit of momentum and will due to the FT code itself not being GPL'd, and scrapped the whole thing.

Basics of FreezeTag (as a gamemode):

• Round-based, team-based mode (so everything that can affect Elimination and/or CTF Elimination is fair game for FT)
• Players get frozen instead of killed by weapon fire.
  • Level hazards (lava, slime, void... even water?) kill players as usual.
  • Frozen players are displayed with a shader covering the entirety of their body (leilei did a frozen shader some days ago).
  • In CTF Elimination, frozen players drop the flag.
• Unlike dead players, frozen players can be thawed either on their own (1 HP/s) or with nearby teammates (5 HP/s).
  • A frozen player is thawed once they reach 100 HP/s.
  • Their arsenal is kept intact and they start from the player they were when frozen.
  • Alternatively, players slowly regenerate health (1 HP/s), but have a separate meter indicating the level of thawing (0%..100%). Nearby teammates thaw 5%, regular thawing is 1%. This is more complicated that the HP approach, though.
• Scoring is the same as in Elimination/eCTF. Perhaps as a motivation, players willing to freeze teammates get score (1 point per second) based on the amount of time spent thawing teammates?

Proposed implementation in OA:

• Due to OA already having a lot of gamemodes, it could be implemented instead as an option for Elimination and eCTF. (Using a cvar like elimination_freezetag) Therefore the main check should be G_IsARoundBasedGametype() && G_IsATeamBasedGametype.
• Cvars elimination_ftThawTime and elimination_ftAlliedThawTime determining how much HP the frozen players restore on their own and with teammates.
• HUD:
  • New center messages: has frozen you!, is thawing you, You have been thawed!.
  • New obituaryOutput messages: has been frozen, has been frozen, has been thawed**, has been thawed, .

In theory, this should require few lines of code. However, there's a lot

[The-Gig]

Just a small detail: for those cvar names, maybe "amount" (similar to g_obeliskRegenAmount) instead of "time"? In case they are expressed in hp/sec.

[NeonKnightOA]

FWIW I've opened a skeleton with some basic, yet unimplemented functions here.

It contains two cvars elimination_freezeTag (enables/disables the mode) and elimination_freezeTag_thawTime (amount of time required to thaw a frozen player). It also contains the helper functions CG_IsPlayerFrozen(*cent) and G_IsPlayerFrozen(*ent) that return true if the player is frozen, and the event flag EF_FROZEN. Plus, the mode is passed through elimFlags to cgame.